Flatbed is quite bad for film scanning and usually even worse for negative film which is sometimes tricky for even the high end film scanners. Epson V700 which is among the best flatbed scanners for film is over your budget and quality is not so good even then, and scanning is slow and cumbersome.
In a budget I'd try to find second hand older dedicated film scanner, like Nikon Coolscan or Minolta.
For new ones, Reflecta and it's rebrands should be better than flatbed -
http://www.scandig.com/filmscanner/reflecta/index.html (there are a lot of good technical reviews on that site about different scanners).